The present invention relates to a novel method of forming an image using a photoconductive material. Particularly, the present invention relates to a method for recording an optical information pattern by selectively causing an ionic reaction in a recording medium by transferring constant charge formed on a part irradiated with light under an electric field.
Heretofore, many methods have been proposed for providing photographs, in a broad sense, for recording optical information, and many of them have been put to practical use in various forms.
Examples of photographic methods widely used at present include silver halide photography, diazo the like. Various modified styles of these methods such as silver halide diffusion-transferring method, diazo type bubble system, electrostatically transferring electrophotography and the like have also been put to practical use. Developments of materials for photochromic photography, thermal photography and the like have also proceeded.
Performances of photographs are generally evaluated in view of the properties of sensitivity, spectral sensitivity (color sensitivity), gradation, resolving power (information density), granularity (S/N ratio), ease of handling, possibility of coloring, and the like. In addition to these properties, other properties such as non-toxicity (non-pollution), the saving of resources, mass productivity, processability, durability, cost and the like should be taken into consideration.
Under these circumstances, there have not been developed materials and systems which satisfy many of the above mentioned performances and properties at the same time.
For example, silver halide photography is notably excellent in sensitivity, and provides satisfactory resolving power and gradation. However, it has the disadvantages that development treatment is complicated and hard to control, and that expensive silver must be used.
Diazo photography is cheap, but the sensitivity to visible light is remarkably low. Therefore, a special light source generating ultraviolet ray is required, and ammonia gas, alkaline solution and the like must be used for development, thus causing handling to be difficult.
In the case of the transfer method of electrophotography, a photosensitive material is repeatedly usable and therefore the running cost is low and its sensitivity is satisfactorily high for practical use. However, since a series of processes such as charging with electricity, exposure, development, transfer, cleaning and the like must be conducted under predetermined conditions, its apparatus is most complicated, and thus the apparatus cost is the highest among the conventional methods. In addition to these disadvantages, the subject to be electrophotographed is limited to a plane copy.
Taking the above mentioned circumstances into consideration, we have found in the process of developing a new electrophotographic material, a method of forming an image using a photosensitizer of basically the same type as the conventional electrophotographic material, but using a novel system fundamentally different from the conventional electrophotographic system. We believe the novel system of this invention is ideal in view of the above mentioned properties and performances.